Device for preventing accumulation of ice on aeroplane propellers



Dec. 6, 1932. f E R 1,889,782

DEVICE FOR PREVENTING ACCUMULATION OF ICE ON AEROPLANE PROPELLERS Filed May 12, 1952 Patented Dec. 6, 19 32 UNITED STATES WILLIAI c. ennn, or I'I'HACA, NEW YORK DEVICE FOR. PREVENTING ACOUIULATION ICE ON .AIEROPLANE PROPELLERS Application filed May 12,

This invention relates to devices for preventing the accumulation of ice on rotating parts such as the propeller blades of an aeroplane, and especially the portions thereof ad- '5 jacent the hub, where the relatlvely slow peripheral speed'permits a relatively large accumulation of ice in the absence of precaution against it.

The chief objects of the invention are cffectiveness, simplicity, lightness and economy. I

Of the accompanying drawings:

Fig. 1 is a side view ofan aeroplane propeller and a preferred embodiment of my invention associated therewith, adjacent portions of the aeroplane being shown in outline.

Fig. 2 is a fragmentary side elevation of the propeller hub and ad acent parts.

Referring to the drawing, the device, in

the particular form here shown, comprises a sleeve or annulus 10 of vulcanized rubber com osition loosely surrounding the base portlon of the propeller blade 11 and fitting about the end flange 12 of the blade-clamp 13 and secured thereto as by a winding of wire 14.

In the rotation of the propeller the centrifugal force of the rubber sleeve causes it to stretch lengthwise of the blade and lessening of the speed causes it to retract, so that its surface may readily be varied in area during flight, with the result that ice forming upon the rubber surface is broken into small particles and dislodged therefrom.

Rapid periodic deformation or vibration of the sleeve also may be eifected by the air stream at some speeds of the propeller and of the aeroplane.

As the sleeve 10 shieldsthe base portion of the blade and thus prevents the formation of ice thereon such ice as forms on the blade farther out does not have such cumulative anchorage of ice nearer the hub as to hold it against centrifugal force and the sleeve thus causes adjacent portions of the blade as well as the portions directly underlying the sleeve to keep free of excessive ice accumulation.

The adhesiveness of the rubber sleeve with relation to ice preferably is reduced by'mixing into the rubber composition before its 1932. Serial No.610,889.

vulcanization, or applying to it after vulcanization and from time to time during its period of service, if necessary, a fluid or other substance adapted to exude from the pores of the rubber, especially at low temperatures, to form a water-repellent or non-freezing film upon the rubber adapted to prevent adhesion o the ice.

As discussed in my copending applications Serial Nos. 465,970 and 466,049, both filed '00 July 7,1930, and Serial No. 534,293, filed May 1, 1931, the water-repellent material to be used for impregnating the rubber preferably is a liquid and the liquid to be used for this purpose should be one which has a freezing point below the ice-forming temperatures and which is fluid at these temperatures. It should be of low viscosity at these temperatures and should not be sticky, and hence adhesive toward ice. It should also be material which will be absorbed into the rubber, but which will not swell or weaken the rubber to such an extent that it would have insuflicient tensile strength for the use to which it is a plied. It is also important that the liquid of relatively high boiling point in order that it may not evaporate from the surface at the highdtemperature' to which it may be subjecte It is desirable that the liquid be such that it may be applied to the rubber without substantlally deteriorating the rubber surface; that it will reduce the adhesion ofthe'ice to the surface. and yet will not evaporate from the surface at ordinary temperatures; that the rubber will have a substantially dry surface'at ordinary temperature s; and that it will exude from the rubber at ice-forming temperatures.

A large number of oils are absorbed into vulcanized rubber,'but ordinarily with the result that 'the rubber is thereby caused to swell to a greater or less extent and conse' quently its tensile strength and other physi-. cal properties are more or less weakened. Because of this effect it has been generally considered to be undesirable to use most oils in contact with rubber.

' I have found that by mixingwith an oil which will be absorbed into the" rubber sur- Freezing point Boiling point Tetrahydronapthalene 25 0. 206 C Dekahydrouapthalene 125 C. 193.3 0 Pine oil 25 C. 150185 C Ethyl benzoate 34. 6 C- 213. 2 C p-cymene 73. 5 C 176. 6 C Castor oil 12 0. above 300 C Lubricating oil from petroleum selccted for low freezing point -15 0 above 250 C.

The addition of one of these liquids to vulcanized rubber will, however, cause the rubber to swell and will decrease its tensile strength. By adding a liquid such as diethyl phthalate or butyl tartrate to one of the above oils, the swelling of the rubber and the decrease in tensile strength will be greatly reduced. If the two liquids to be mixed are not miscible with each other, they may be brought into common solution by adding a liquid capable of dissolvin both of them. For example, diethyl phtha ate and pine oil, which are mutually immiscible, may be brought into solution by adding castor oil, which in itself is'insoluble in rubber and therefore further reduces the swelling of the rubber.

As an example of a suitable composition to be applied to arubber surface, and which will reduce the adhesion of ice to the rubber surface, the following substances may be mixed in the proportions stated Parts by volume Pine oil 4 Diethyl phthalate 4 Castor oil 1 This particular mixture has the added ad-. vantage that its solubility in rubber is reduced at the ice forming temperatures, so that at these temperatures it will exude from and render the surface well lubricated while it will composition Parts Smoked sheet 100 Zinc oxide 10 Sulfur 3 Accelerator 1 When the oil is added to the vulcanized rubber to reduce the adhesion of ice to the 1 surface, the rubber mixture should be one, 1 such as the above, with little or no oil soluble sticky material that would render the surface adhesive to ice. Some other colloidal surface may be used in place of rubber, if the surface is to be one that is devoid of irregularities into which water might penetrate and, upon freezing, anchor itself.

When a vulcanized rubber of the above described composition is soaked in pure pine oil for 24 hours, its average increase in volume will be greater than 50%, and its average decrease in tensile strength will be greater than 75%. However, when a vulcanized rubber of the same composition is soaked for 24 hours in the mixture of oils referred to above, it was found to have an increase in weight of about 19%, an increase in gauge or volume of about 7 and an average decrease in tensile strength of about 12 75. It is apparent, therefore, that although an appreciable weight of oil had been absorbed into the rubber, the volume had been only relatively slightly increased and the tensile strength had been but moderately affected.

Although I have described a particular mixture of liquids, it is not intended to thereby limit the mvention to the specific liquids or proportions mentioned. Other vegetable,

mineral or synthetic oils may be used to give the desired lubricating or reduced adhesion characteristics. Other liquids than those described may also be added to such oils to reduce the swelling of the rubber and the resultant decrease in tensile strength and deterioration of other physical properties. Such liquids maybe alcohols, ketones and other esters whichpossess the property of mixing with nitrocellulose or, as hereinbefore indicated, castor oil. freezing point may be unimportant in the particular use to which the liquids may be applied, in which event a wide range of selection may be had. Furthermore the particular oil added for this purpose may not come within the range of temperatures desired, although the resultant mixture may be within that range.

Modifications are possible within the scope The boiling point and of the invention as defined in the appended claims.

I claim:

1. In combination with. a rotary member exposed to ice-forming conditions, a deformable shield so associated therewith as to be deformed by centrifugal force.

2. In combination with a rotary member exposed to ice-forming conditions in an air stream, a deformable shield so associated therewith as to be deformed by the air stream and by centrifugal force.

3. In combination with a rotary member exposed to ice-forming conditions in an air stream, a deformable shield so associated therewith as to be deformed by the air stream.

4. In combination with a rotary member exposed to ice-forming conditions a porous member so associated therewith as to be deformed by centrifugal force and an adhesionreducing material in the pores of said porous member.

5 In combination with a rotary member exposed to ice-forming conditions a rubber member so associated therewith as to be stretched by centrifugal force.

6. In combination with a rotary member exposed to ice-forming conditions a rubber member so associated therewith as to be stretched by centrifugal force and adhesionreducing material on the surface of the said rubber member.

7. In combination with a part of an aerolane to be protected from accumulation of Ice thereon, a deformable shield associated therewith and so constructed and arranged as to be automatically deformed by forces normally incident to flight of the plane.

8. In combination with a part of an aero plane to be protected from accumulation of ice thereon, a rubber shield associated therewith and adapted to be stretched by centrifugal force, and means for rotating said rubber member.

In witness whereof I have hereunto set my hand this 9th day of-May, 1932.

WILLIAM C. GEER. 

